Extraction of zinc



Patented Sept. 26, i922. 7

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'WARING, OF VJEBB CITY. MISSOURI, ASSIGNOR E ONE-HALF TO GORDON BATTELLE, 0F COLUMBUS, OHIO.

EXTRACTION OE ZINC.

No Drawing.

and tate of Missouri, have invented certain -new and useful Improvements in the Extraction of Zinc, of which the following is a s ecification.

. his invention relates to the extraction of zinc; and it comprises-an improvement in methods of extracting zinc from roasted ores, oxidized fumes, and the like by the action of hot solutions of ammonium sulfatewherein the basic sulfate of zinc precipitated on cooling such solutions is treated with a solution containing the calculated amount of ammonium carbonate to form basic carbonate of zinc and ammonium sulfate solution which can be returned to the extraction operation all as more fully hereinafter set forth and as claimed.

In various metallurgical processes treating complex ores in furnaces of the type of the Scotch hearth, the \Vetherill furnace, as well as in various reverberatory type furnaces used in roasting and smelting ores, there is a production of oxidized flue dust or taining lead and zinc as Well, usually, as various other metals and elements. The lead and zine-are contained in the form of oxi dized compounds, such as oxids. sulfates, sulfides, etc. Roasted sulfid ores containing lead and zinc are, or may be, of analogous composition and contain zinc and lead in fifi oxidized form. Various other technically available materials also contain lead and zinc in oxidized form. Many methods have been proposed, and some are in use, for treating materials of this type for the purpose of 40 separately recovering the lead and zinc as well as other metals. Some of these methods depend, in principle, upon the fact that the solubility of zinc compounds in a hot strong solution of ammonium. sulfate is greater than in a cold solution, while lead compounds are substantially insoluble in the hot solution so that a solution saturated while hot deposits zinc compounds pn cooling. In these methods the fume or analogous material is digested with" a hot strong solution of ammonium sulfate, the solution separated from the residue and cooled, whereupon there is a. depositiom or precipitation of material consisting of or containing basic sulfate'of zinc. The exact character of this fume con-v Application filed August 17, 1921. Serial No. 4:93,132.

deposited material depends upon the circumstances; the strength of solution, the temperature, etc. Using a saturated solution of sulfate of ammonium which is digested with the material at about the normal boiling point or a little above removed and cooled to 50 to 70 C., the de osition is substantially composed of a basic sulfate of zinc having the empirical formula 5ZnO, S0,. VVLth other strengths of ammonium sulfate solution,.other temperatures, etc., the deposit is of a different character, sometimes carrying ammonium sulfate and sulfates of various other metals than zinc. Not all the zinc is deposited in so cooling the liquid but as the liquid goes back for use in extraction, this fact isimmaterial.

In a practical embodiment of this method treating roasted ore, oxidized fume. etc.., carrying lead and zinc, the material is digeste'd with an ammoniiun sulfate solution from a previous operation and carrying a certain amount of dissolved zinc compounds. The solution and the fume are heated together, this being best done under some pressure. Any ammonia liberated in this operation is caught and collected in suitable ways. After digesting for an hour or thereabouts,

the charge is withdrawn from the,digester and the solution se )arated from the solid residue in any suita 1e way. The material from the digester may be simply filterpressed using a heated press. The residue or prom cake is submitted to other treatments not here important, including a washing with strong ammonium sulfate solution. The washings serve in making up liquor for another digestion. The hot liquor expressed from the cake is run through a hot chamber filled with shot zinc, zinc scrap, etc. This precipitates silver cadmium. copper, or any other easily reduciblemetal Which may be present. The hot purified liquor is then cooled in any suitable way to about 50 to C. It may, for example, be run into a jacketed tank and stirred. An advantageous way is to spray it into a chamber, producing the desired'cooling byself-evaporation. The solid material separated on so cooling is a substantially pure basic sulfate of zinc of the indicated composition. Other ways of extracting the material with hot sulfate of ammonia solutions. as stated. give solutions depositing zinc-containing precipitates on cooling, but these precipitates are form.

also amenable to treatment under the present purposes. It has exceptionally g invention.

The basicsulfateof zinc and other zinccontaining precipitates produced in these methods of Xtracting Zinc are not in themselves marketable materials and they are somewhat difficult to work into merchantable The sulfuric acid present cannot readily be eriven off by simple heating with production Zinc oxide or the like.

lit is the object of the present invention to provide a method whereby basic sulfate of zinc etc. produced in th described manner may be readily converted into high grade materials of marketable nature with an incident economy in the process as a whole.

Considering the basic sulfate zinc SS produced in the method above described, while it does not contain other metals, it noes contain a considerable amount of adhering ammonium sulfate solution; this solution in turn containing unprecipitated, dissolved zinc compounds. The ammonium sulfate may, of course, atleast to a large extent, be'recovered by washing with water, but since on dilution the adhering; a .imonium sulfate solution the contained zinc is partially precipitated, there is some in convenience in manipulation. tl e present method l take the unwashed press cake, still containing a. certain amount of mother liquor, and treat it with a solution of monium carbonate containing the amount hll-l, corresponding to thev SQ combined with zinc. lVith greater proportions of monia, more or less zinc goes into solution; with less amounts, some St), is not removed from the precipitate. The press cake is agitated or otherwise brought into effective contact with the ammonium carbonate solution. A smooth reaction takes place by which the basic zinc sulfate is converted into basic zinc carbonate with formation of sulfate of ammonia. This sulfate of ammonia, together with that of the mother liquor, goes into the solution. The initial contact may be cold, but it is usually best to heat the mixture to boiling, least in finishing, as this. facilitates subsequent filtration and washing. After the'reaction is accomplished the mixture is put through a filter press, or otherwise treated, to separate the solid from the liquid, the solid basic zinc carbonate being washed with water in the usual ways. The ammonium sulfate solution goes back to the extraction process. The washings are concentrated to give a strong solutionof ammonium sulfate or are heated with lime to recover the ammonia.

The washed basic zinc" carbonate is sub stantially free of and NH, and is a material-which, by reason of its physical state, is excellently w ell adapted for pigmentary .ing power and makes a very good oil pa at. If desired, it may be roasted or calcined at a low temperature to convert into oXid of zinc; this oxid of zinc being also of good pi gmentary, quality and being, because of its fine subdivision, well adapted for use j filler in a rubber manufacture, etc.

ln applying the present method to precipitates which are not, like just described, merely basic sulfate of zinc, analogous results are secured. Any sulfate of ammonia occurring in double salts is of course extracted. Any other metal which ma occur as an im'ourit in the recioitated a. o .L A

basic zinc sulfate, or basic zinc sulfatecoinposition, is also extracted.

Tn the described invention, it will 'be'noted, l have provided method of cheaply and readily converting basic Zinc sulfate. extracted from roasted ore, fume and the lilze by these methods, into a etable material with recovery solvent material suitable for re-use in'the en'trac 'on process.

@rdinarily, these materials contain enough to lreep the sup y of sulfate of ammonia replenished, il here they do not, sulammonia to be used in the'step of treating the proof sulfate of zinc.

recovery of zinc, the process which comprises leaching a material containing Zinc in oxidized form with a hot saturated solution ammonium sulfate containing zinc sulfate, cooling the solution to precipitate basic sulfate of zinc, treating the pre cipitated sulfate of zinc with'ammonium carbonate solution in the proportion necessary to form ammonium sulfate with the sulfuric acid present, separating the carbonate ti l . fate of ammonia is added from time to time ltlll of zinc produced and returning the ammonium sulfate solution for re-use in the ing said solution, the process which comprises reacting on said zinc compounds with ammonium carbonate solution to convert said zinc compounds into a zinc carbonate form ammonium sulfate solution. In testimony whereof, I have hereunto affixed my signature.

WTLLTAIVT GEURGE Wllldllll, 

